Re: [PATCH v3 1/4] mm: update the memmap stat before page is freed

Fan Ni
2024-08-08T17:18:22Z

On Thu, Aug 08, 2024 at 03:42:34PM +0000, Pasha Tatashin wrote:
> It is more logical to update the stat before the page is freed, to avoid
> use after free scenarios.
>
> Fixes: 15995a352474 ("mm: report per-page metadata information")
> Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> Reviewed-by: David Hildenbrand <david@redhat.com>

Reviewed-by: Fan Ni <fan.ni@samsung.com>

> ---
> mm/hugetlb_vmemmap.c | 4 ++--
> mm/page_ext.c | 8 ++++----
> 2 files changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
> index 829112b0a914..fa83a7b38199 100644
> --- a/mm/hugetlb_vmemmap.c
> +++ b/mm/hugetlb_vmemmap.c
> @@ -185,11 +185,11 @@ static int vmemmap_remap_range(unsigned long start, unsigned long end,
> static inline void free_vmemmap_page(struct page *page)
> {
> if (PageReserved(page)) {
> - free_bootmem_page(page);
> mod_node_page_state(page_pgdat(page), NR_MEMMAP_BOOT, -1);
> + free_bootmem_page(page);
> } else {
> - __free_page(page);
> mod_node_page_state(page_pgdat(page), NR_MEMMAP, -1);
> + __free_page(page);
> }
> }
>
> diff --git a/mm/page_ext.c b/mm/page_ext.c
> index c191e490c401..962d45eee1f8 100644
> --- a/mm/page_ext.c
> +++ b/mm/page_ext.c
> @@ -330,18 +330,18 @@ static void free_page_ext(void *addr)
> if (is_vmalloc_addr(addr)) {
> page = vmalloc_to_page(addr);
> pgdat = page_pgdat(page);
> + mod_node_page_state(pgdat, NR_MEMMAP,
> + -1L * (DIV_ROUND_UP(table_size, PAGE_SIZE)));
> vfree(addr);
> } else {
> page = virt_to_page(addr);
> pgdat = page_pgdat(page);
> + mod_node_page_state(pgdat, NR_MEMMAP,
> + -1L * (DIV_ROUND_UP(table_size, PAGE_SIZE)));
> BUG_ON(PageReserved(page));
> kmemleak_free(addr);
> free_pages_exact(addr, table_size);
> }
> -
> - mod_node_page_state(pgdat, NR_MEMMAP,
> - -1L * (DIV_ROUND_UP(table_size, PAGE_SIZE)));
> -
> }
>
> static void __free_page_ext(unsigned long pfn)
> --
> 2.46.0.76.ge559c4bf1a-goog
>